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Show 234 DR. A. GUNTHER ON NEW AMERICAN FISHES. [Mar. 26, ample, 22 inches long, at Xeberos. It has no adipose fin ; therefore Kner's assertion, that the absence of this fin in the typical example is merely accidental, is not confirmed. HYPOPTOPOMA (g. n. HYPOSTOMATINUM.). This genus differs from Plecostomus in the peculiar formation of the head, which is depressed, spatulate, the eyes being on the lateral edge of the head. The moveable gill-covers are reduced to two bones, viz. the operculum, small and placed as in Plecostomus, and a second, larger bone (interoperculum 1), separated from the eye by the narrow suborbital ring, and placed at the lower side of the head. Fig. 2. Hypoptopoma thoracatum. H Y P O P T O P O M A T H O R A C A T U M . (Fig. 2.) D. -i/l. A. 6. P. 1/6. V. 1/5. L. lat. 24. The form of the head approaches that of Loricaria, being much depressed ; the snout broad, with the outline elliptical. The interorbital space is slightly convex, but little narrower than the greatest width of the head, which is three-fourths of its length. The |